A method for excavation and loading by means of a bucket of a conventional front-end loader will be explained with reference to FIG. 1. FIG. 1 is a side view of a wheeled front-end loader. A front-end loader 1 has a working machine 5 equipped with a boom 3 and a bucket 4 at the front portion of a vehicle body 2. The front-end loader 1 mainly performs an operation of excavating a load 6 such as crushed rocks or earth and sand, and loading the same into a dump truck or the like. The operation of the working machine 5 of the front-end loader 1 includes a boom operation and a bucket operation. An operation of excavating and loading the load 6 into the bucket 4 is carried out by alternately performing a boom raising operation and a bucket tilting (in an ascending direction) operation while moving the front-end loader 1 toward a pile of the load 6.
In the above conventional excavation and loading operation by means of the bucket, an operator manipulates the boom operating lever and the bucket operating lever while moving the vehicle (the front-end loader) forward to alternately perform a boom raising movement and a bucket tilting movement, thereby loading the load into the bucket. In this situation, the operator controls the boom angle and the bucket angle by his or her intuitive knowledge. The relationship between the boom angle and the bucket angle differs depending on the earth quality of the load, loading operation conditions, or the like, and has a great influence on the operation efficiency. Accordingly, the operation requires a considerably high level of skill and experience, and the quantity of load loaded into the bucket varies according to the skill of an operator, thus reducing working efficiency with unskilled operators. However, there is a disadvantage that it is difficult to secure skilled operators. In addition, there arises a disadvantage that even skilled operators find it troublesome to alternately perform the boom raising operation and the bucket tilting operation, therefore causing fatigue and reducing efficiency.